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wiring two gang two way light switch

Posted: Thu Dec 18, 2008 4:02 pm
by alex6192
Hi guys,

I am trying to replace two light switches for dimmers.

Both switches are two way.

One of the switches has three wires and the other has two.

Each of the wires have three inner wires (excluding the bare earth) and they are coloured black, grey and brown. One of the main wires (the 3 wire box) has 'switched feed' written on it. All the other wires are unmarked.

The dimmer switch I have bought (which i intend to fit onto the box which has three wires coming from it) has two L1 terimnals, two L2 terminals and two which have a symbol that looks like a wavy line with an arrow going through it.

So, in summary I have the following.

Box 1 (excluding earth).

3 black wires
3 grey wire
3 brown wires

Box 2 (excluding earth):

2 black wire
2 grey wires
2 brown wires

Switch 1 (for box 1)

2 L1 terminals
2 L2 terminals
2 wavy line terminals

Switch 2 (for box 2)

2 L1 terminals
2 L2 terminals
2 COM terminals

Can anyone tell me how to wire these switches?

Many thanks,

Posted: Fri Dec 19, 2008 4:35 pm
by ericmark
I will assume you have double two way switches at both locations?
It would not be normal to have 3 x triple and earth cables and I would guess who ever wired it bought one drum of cable and where it only required two cables just earthed the unused core. Or if not an electrician just left unused core disconnected.
So I would guess box 1 you have two unused cores and at box two one unused core.
There is no colour code all cores which are line should have brown sleeves and all that are earth should have green/yellow sleeves although in real terms it is unlikely the brown sleeves were ever fitted.
Before disconnecting you need to make careful note of which wires go to com.
Also in your case which wires go to earth, or no where.
Each cable will only connect to one switch.
Therefore in box one there will be two cables going to one switch and one to the other.
Non two way switch will have one wire to com and one to L1
The two way switch will have one wire to com and two wires to both L1 and L2 of the two wires going to L1 there will be one from each cable the same with L2.
You will have two unused wires.
With box two one cable will go to one switch using all three connections and the other will only use com and L1 connections.
In both boxes the colour going to com where all three wires are used will be the same.
The symbol that looks like a wavy line with an arrow going through it is most likely the com on the dimmer switch.
You should only use one dimmer switch on each lamp.
If you need to have one dimmer and one standard two way switch in one box you will need to use grid switches which allow you to mix and match.
If you get L1 and L2 swapped it will not matter so long as the com wire is correct.
If you have not noted the original connections the cables will need ringing out.
There is no standard but looking at my web page may help you understand what you are doing. There are two main methods to wire two way switches I am assuming method 2 as shown at the bottom of my web page.

Posted: Fri Dec 19, 2008 5:16 pm
by alex6192
Sorry, this is a double post, please see the other post of the same name.